V. Correcher

LUMINESCENCE SPECTRA OF ALKALI FELDSPARS: INFLUENCE OF CRUSHING ON THE ULTRAVIOLET EMISSION BAND

Abstract Grinding and milling processes lower the intensity of the ultraviolet emission band of alkali feldspars. The luminescence spectra of aliquots of natural transparent adularia from Saint Gothard, Switzerland, that were crushed at different energies, show the irreversible collapse of the UV 290 nm peak. Simultaneously, the 390 nm blue emission increases in accordance with the milling treatment, which reduces the presence of ionic charge compensators (Na+) and sensitizes the structure (producing [AlO4]° centers). The annihilation of the 290 nm UV peak by crushing could be linked with cracks-strain-exsolution features of the lattice of adularia. For this reason, the use of this 290 nm peak and energetic milling treatments in dating and dosimetric routines, should be rejected.

On the use of natural quartz as transfer dosemeter in retrospective dosimetry

A new and simpler stabilization procedure for natural quartz for use as a transfer dosemeter is presented. Stabilization of the thermoluminescence signal of the dosemeter is attained through a single irradiation to a high dose 90 Gy and one annealing at 550°C for 30 min. A reliable saturation of the pre-dose sensitization effect for the high temperature peaks, 220 and 325°C, of quartz, permits one to obtain good stability upon reuse.

Absorbed dose evaluations in retrospective dosimetry: methodological developments using quartz

Abstract Dose evaluation procedures based on luminescence techniques were applied to 50 quartz samples extracted from bricks that had been obtained from populated or partly populated settlements in Russia and Ukraine downwind of the Chernobyl NPP. Determinations of accrued dose in the range ∼30–300 mGy were obtained using TL (210°C TL and pre-dose) and OSL (single and multiple aliquot) procedures. Overall, good inter-laboratory concordance of dose evaluations was achieved, with a variance (1 σ ) of ∼±10 mGy for the samples examined.

Dose dependence and fading effect of the thermoluminescence signals in γ-irradiated paprika

The thermoluminescence (TL) method can be used to discriminate irra- diated and non-irradiated paprika. This study reports the polymineral composi- tion of the dust adhered to paprika; radiation-speci-c luminescence is emitted by the inorganic material (mainly quartz, feldspars and calcite). On the basis of the shape of the TL curves (or glow curves) some physical parameters are evaluated. Natural TL curves, from non-irradiated samples, show three very low intensity peaks while induced TL curves, from irradiated paprika, seem to consist of -ve overlapping peaks. TL spectra reveal a very important di†erence in intensity and in the position of the peaks between irradiated and non-irradiated paprika. Fading observations of TL after irradiation at 5, 10 and 21 kGy, show the same behaviour in all the cases: an initial rapid decay to maintain a certain stability from 300E400 h onwards. 1998 SCI. (

Luminescence of α-Al2O3 and α-AlOOH natural mixtures

Abstract Natural mixtures of sapphire (α-Al2O3) and diaspore (α-AlOOH) samples from Goian (NW Spain) have been analysed by scanning electron microscopy, electron microprobe, spectral luminescent techniques (thermoluminescence, radioluminescence, cathodoluminescence) and inductively coupled atomic plasma bulk analyses. Blue coloured areas could be attributed to chromophore elements (FeO=0.278%, TiO2=0.023%) and the large photon emission peak observed at 700 nm with 80 ppm of Cr2O3. Additional smaller bands at 670 and 720 nm can be assigned to Ti4+ and FeO in the lattice. The coexistence of two different types of luminescent behaviour in the lattice of this material, such as a discrete electron trap distribution at lower temperature (circa 190°C) and a continuous trap structure at higher temperature (over 250°C) and their relationship with dehydroxylation and chromophore oxidation are explored.

Analysis of luminescence spectra of leucite (KAISiO4)

High-sensitivity radioluminescence (RL) and thermoluminescence (TL) measurements were carried out on samples of natural leucite (with 2.95% of Na2O) from Campania Vessa (Italy). Samples were annealed to modify the charge compensation through alkali metal self-diffusion and to produce luminescence centres. High-temperature powder diffraction, scanning electron microscopy and chemical analyses were performed to monitor the tetragonal-cubic phase transitions and the thermal drainage of alkali metal ions from the aluminosilicate lattice. The emission spectral bands of leucite (300, 380, 430, 480, 560 and 680 nm) match those of other Na/K-aluminosilicates (alkali metal feldspars) and could be attributed to similar defects. TL glow curves of increasingly pre-irradiated natural leucite (range 0-20 Gy) showed no changes above 300 degrees C, whereas some changes were observed with annealed samples (1000 degrees C for 12 h). This temperature is the starting point of Na self-diffusion within the aluminosilicate lattices. The areas of the TL glow curves of both natural and annealed beta-irradiated leucites can be fitted with a linear function with high correlation. These results are in agreement with high alkali metal loss (K2O approximately 12% and Na2O approximately 18%) during thermal pre-treatment, high cell volume expansion (from 2350 to 2500 A) and the cubic la3d reversible tetragonal I4l/a phase transition. This promotes the egress of alkali metal ions and the production of [AlO4/M+]o, [AlO4/H+]o and [AlO4]o luminescence centres.

Thermal and electron stimulated luminescence of natural bones, commercial hydroxyapatite and collagen

The luminescence (cathodoluminescence and thermoluminescence) properties of natural bones (Siberian mammoth and adult elephant), commercial hydroxyapatite and collagen were analyzed. Chemical analyses of the natural bones were determined using by Electron Probe Micro-Analysis (EMPA). Structural, molecular and thermal characteristics were determined by X-ray Diffraction (XRD), Raman spectroscopy and Differential Thermal and Thermogravimetric analysis (DTA-TG). Cathodoluminescence (CL) spectra of natural bones and collagen showed similar intense broad bands at 440 and 490 nm related to luminescence of the tetrahedral anion [Formula: see text] or structural defects. A weaker luminescence exhibited at 310 nm could be attributed to small amount of rare earth elements (REEs). Four luminescent bands at 378, 424, 468 and 576 nm were observed in the commercial hydroxyapatite (HAP). Both natural bones and collagen samples exhibited natural thermoluminescence (NTL) with well-defined glow curves whereas that the induced thermoluminescence (ITL) only appears in the samples of commercial hydroxyapatite and collagen. Additional explanations for the TL anomalous fading of apatite, as a crucial difficulty performing dosimetry and dating, are also considered.

Thermo- and cathodoluminescence properties of lepidolite

Lepidolite, K(Li,Al)3(Si,Al)4O10(F,OH)2, and many of the related phyllosilicate mineral of the mica group have been well studied from the chemical and structural point of view; however, to the best of our knowledge, studies on their luminescence properties have been scarcely reported. This work focuses on the thermoluminescence (TL) and cathodoluminescence (CL) response of a natural lepidolite from Portugal previously characterized by means of environmental scanning electron microscope (ESEM) and X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS) techniques. The complexity of the thermoluminescence glow curves of non-irradiated and 1 Gy irradiated samples suggests a structure of a continuous trap distribution involving multiorder kinetics. UV-IR CL spectral emission shows seven peaks centered at 330, 397, 441, 489, 563, 700, and 769 nm. Such emission bands could be due to (i) structural defects, i.e., [AlO4] or non-bridging oxygen hole centers and (ii) the presence of point defects associated with Mn(2+) and Fe(3+).

Study of the thermoluminescence emission of a natural α-cristobalite†

The thermoluminescence (TL) properties of a well-characterised natural α-cristobalite from Lanzarote (Canary Islands, Spain) have been studied. The natural blue emission (at 400 nm) of this silica polymorph of quartz reveals the appearance of three groups of components peaked at 150, 230–240 and 370 °C, which could be associated, respectively, with (i) structural defects (similar to quartz), (ii) the reversible phase transition from α-cristobalite to β-cristobalite and (iii) electron recombination with unstable holes trapped at oxygen vacancies next to Al ions linked to the formation of β-cristobalite. Similar to quartz, the induced TL (ITL) glow curves display four maxima, peaked at 90, 110, 180 and 220 °C, which could be respectively associated with (i) oxygen vacancies, (ii) recombination of electrons with (H3O4)° centres that can act as hole traps, (iii) [GeO4]− centres that are stabilised with monovalent cations (H+, Li+ or Na+) and (iv) [AlO4]° hole-like centres that are created when alkali ions are moving away from Al sites related probably to the reversible phase transition. The dose dependence of the ITL emission of β-irradiated samples at room temperature exhibits a linear increase in the glow intensity of the 180 °C maximum when increasing the dose (r=0.997) in the range 0.5–10 Gy. †Paper presented as a contribution to the 10th International Symposium on Solid State Dosimetry, Mexico City (24–28 September 2007).

Effect of heating rate on the thermoluminescence and thermal properties of natural ulexite

Boron-rich compounds are of interest in the nuclear industry because they exhibit a high neutron absorption cross section. The manufacture of these materials involves the application of thermal and chemical treatments. This paper focuses on the study of the effect of the heating rate (HR) in two thermal techniques, differential thermal analysis (DTA) and thermoluminescence (TL), performed on natural ulexite from Bigadiç-Balıkesir (Turkey). The TL measurements were performed at six different heating rates in the range of 25-240°Cmin-1. The UV-blue TL emission of natural ulexite shifted toward higher temperatures with increasing heating rate, whereas the intensity decreased. The kinetic parameters of the ulexite (Ea=0.65(9) eV and s=1.22×1012s-1) were calculated using the variable heating rate method. DTA measurements performed in the range of 0.5-10°Cmin-1 displayed similar behavior to that of the TL response, despite the differences in technique and HR values. The DTA results indicated that natural ulexite exhibits two endothermic peaks originating from different processes: (i) a phase transition between the pentahydrated ulexite phase and a triple-hydrated phase and (ii) dehydration, dehydroxylation and alkali and earth-alkali self-diffusion processes in the ulexite lattice. The main endothermic peak shifted from 160°C to 250°C as the heating rate was increased.